There is an opinion, that working with certified specialists is paying a dispensable overhead. However, sometimes it is the only way to be sure, that your project will be done without overuse of resources, by the planned date and quality.
In our team we have certified Sitecore developers. Each of them has a personal certificate.
The general process of certification looks like training. Usually it lasts for about three days. The sitecore architect comes to your office. This training is the last option to get answers before the test. Besides there is right time to discuss the best practices and uncommon situations. If the test is passed, an applicant gets a certificate. However, this is just the first step in the long process of the non-stop education.